During the production of hot strip by means of a hot rolling train, the hot strip is generally coiled up on a coiler to form a hot strip coil at the end of the hot rolling train. In this case, the hot strip has generally already passed through a cooling section, in which the desired microstructure of the hot strip and therefore the properties thereof have been set. Examples of metals which undergo such processes are steel, aluminum and copper. However, other strips of different metals are also processed in hot rolling trains.
Particularly in the case of microstructures of modern metal qualities, in particular of steel, aluminum and copper, it may be found that the metallurgical properties thereof also change even after the actual hot rolling. By way of example, the cooling of the hot strip coil may be accompanied by instances of local hardening of the hot strip coil on the coil store which, in a subsequent cold rolling process for said hot strip coil, can result in barely controllable disruption to the strip quality of said metal strip. In particular, such disruptions occur cyclically with a variable period duration as a result of the unwinding of the hot strip coil, caused by the coil circumference changing during unwinding. As a result of such cyclic hardness fluctuations, it is possible, for example in multi-stand cold rolling mills, in particular tandem rolling mills, for self-energizing vibrations to arise, which have a negative influence on the strip quality of the metal strip to be produced.
In order to avoid this problem of self-energizing vibrations in the case of multi-stand cold rolling trains, provision can be made, by way of example, for metal strips of such sensitive metal qualities to be rolled on a single-stand cold rolling mill.
However, this results in an increased rolling time for each metal strip, in order to achieve the final dimensions of the respective metal strip, and is therefore disadvantageous from an economical point of view compared to rolling of the metal strip in a multi-stand cold rolling train.
Laid-open specification DT 24 50 548 A1 discloses a cooling apparatus for rolled stock, in particular strip coils, which are cooled with the aid of gondolas which occasionally move through a trough of cooling liquid. This solution takes up a large amount of space and is unsuitable for the requirements of modern metal qualities.
U.S. Pat. No. 4,869,089 discloses an apparatus which prevents the discharge of heat from the hot strip coil by virtue—if a predefined temperature difference between an outer and an inner layer of the hot strip coil is exceeded—of a thermally insulating cover, so that the cooling rate of the outermost layer of the hot strip coil is reduced. This document therefore deals with relatively large-area—with respect to the strip length—temperature disruptions when cooling hot strip coils during the intermediate mounting thereof.